I think it really depends on the kids. Some are interested in interacting with others earlier, and some aren't. It's quite normal for kids to not really start interacting with other kids the same age till 2 or older.

I don't think you can really teach them to socialise or interact, they can and will only do it when they're ready. But you can give him opportunities to play around other kids, like playgroup or whatever, and just see how that goes. Maybe he's a bit young for organised activities like the library or whatever, so situations where he can just free play might work better for now?

I do think it's a good idea for you to get out and meet with other adults, too, if you're not doing that much. And your DS can have a play at the same time.